This invention is in the field of manufacturing books and particularly in the stage where a flyleaf is adhered to the end sheets of a book insert or book block following the perfect binding stage and before the casing-in stage. The flyleaf is basically a reinforcing sheet wrapped around the spine and overlying part or all of the end papers and adhered thereto by adhesive. In one prior art technique for adhering a flyleaf, liquid adhesive was applied to one or other of the adhering surfaces by rollers, followed by contact of other pressure rollers intended to evenly distribute the adhesive between the adhered surfaces. The use of liquid adhesive has a great variety of inherent drawbacks over and above the burden of containing, applying and distributing adhesive to the appropriate surfaces. Frequently excess glue seeps out onto edges of the book or onto parts of the apparatus; also there may develop air pockets surrounded and trapped by adhesive leading to bubbles beneath the flyleaf and/or torn flyleaf. A significant improvement in this stage of book manufacture has been the development of pre-glued flyleaf sheets which have on the inside surface a dry layer of hot melt adhesive, i.e., heat sensitive material which will soften, melt and become tacky upon subsequent application of heat thereto. With this kind of flyleaf preparation the only basic requirement is that heat and pressure be applied to the outer surface of the flyleaf which is wrapped around the book insert, until the adhesive melts and the overlying surfaces adhere to each other. Heat and pressure are applied by heated rollers or other means. An inherent problem herein, leading to loss of time and loss of product has been non-uniform melting of the hot melt adhesive surface with consequences as described above and subsequent non-uniform cooling and warpage of the resultant products which are typically piled into stacks to cool and return to ambient temperature.